1. Field of the Invention
The present invention relates to an image pickup unit, an optical unit, and a manufacturing method for the image pickup unit.
2. Description of the Related Art
An electronic endoscope, a cellular phone with camera, a digital camera, and the like including an image pickup unit provided with a solid-state image pickup device such as a CCD or a CMOS are being widely spread.
A main section of the image pickup unit includes the solid-state image pickup device and an optical unit including a lens for making an optical image of a subject incident on a light receiving section of the solid-state image pickup device. In the cellular phone with camera and the digital camera reduced in size and thickness or the electronic endoscope adapted to view sideways and reduced in diameter of an insertion section, for the purpose of, for example, bending an optical axis or realizing a reduction in thickness of the image pickup unit, the optical unit further includes a bending optical element such as a prism. The image pickup unit in which the optical unit includes the bending optical element is disclosed in, for example, Japanese Utility Model Laid-Open No. Hei 7-24088.
As shown in FIG. 1, a main section of an image pickup unit 65 disclosed in Japanese Utility Model Laid-Open No. Hei 7-24088 includes an optical unit 68 and a solid-state image pickup device 64. A main section of the optical unit 68 includes a lens unit 62 and a prism 63. A main section of the lens unit 62 includes a lens barrel 62c, a first lens unit 62a and a second lens unit 62b including plural lenses provided in the lens barrel 62c, and a coupling frame 62d fit in an outer circumference on a rear end side in an optical axis direction of the lens barrel 62c. 
An incident surface 63a of the prism 63 is bonded and fixed to a rear end in the optical axis direction of the coupling frame 62d. The solid-state image pickup device 64 is fixed to an emission surface 63c of the prism 63.
In the image pickup unit 65 having such a configuration, adjustment of an angle of deviation and centering of an optical system in the optical unit 68 can be realized by alignment adjustment of the two lens units 62a and 62b, the prism 63, and the solid-state image pickup device 64.
However, in the image pickup unit disclosed in Japanese Utility Model Laid-Open No. Hei 7-24088, when the optical unit 68 and the image pickup unit 65 are manufactured, after the prism 63 and the lens unit 62 are separately formed, the prism 63 is bonded to a rear end portion of the coupling frame 62d of the lens unit 62. Since work for adjusting the angle of deviation and the centering of the optical system in the optical unit 68 is difficult and takes long time, the work causes an increase in cost. There is a demand for a manufacturing method that can manufacture a large number of optical units and image pickup units at a time at low cost.
On the other hand, a main section of the image pickup unit includes the solid-state image pickup device and an optical unit including a lens for making an optical image of a subject incident on a light receiving section of the solid-state image pickup device. In recent years, as the optical unit, an optical unit in which optical components are laminated in plural layers is well known. The optical unit is formed by slicing an optical unit wafer after bonding plural lens wafers, which form the optical components such as a lens, a stop, and a spacer, and forming the optical unit wafer.
As the image pickup unit, an image pickup unit is well known which is formed by slicing an image pickup unit wafer after bonding plural lens wafers, which form the optical components such as a lens, a stop, and a spacer, and forming an optical unit wafer and further bonding a sensor wafer including a solid-state image pickup device to the optical unit wafer and forming the image pickup unit wafer.
For example, Japanese Patent Application Laid-Open Publication No. 2004-29554 discloses an image pickup unit 224 formed by, as shown in FIG. 2, bonding an image pickup device 223 to a bottom surface of an optical unit 222 formed by laminating lenses 222a to 222c as optical components in plural layers to have spaces in an optical axis direction in a part between the lenses 222a and 222b and between the lenses 222b and 222c. 
In the optical unit 222 shown in FIG. 2, the optical unit 222 is formed by cutting an optical unit wafer by dicing or the like after bonding a lens wafer including the lens 222a, a lens wafer including the lens 222b, and a lens wafer including the lens 222c and forming the optical unit wafer. As an external shape of the optical unit 222, as shown in FIG. 2, a planar shape viewed from above is often a square shape or a polygonal shape because of a limitation in a processing method.
In the optical unit 222 disclosed in Japanese Patent Application Laid-Open Publication No. 2004-29554, an area functioning as an optical lens, i.e., an area functioning to focus an optical image of a subject on the image pickup device 223 in the optical unit 222, in other words, an area through which a light beam from the subject passes is set to a dimension equal to or smaller than a dimension of a circle C inscribed in a square forming an external shape of the optical unit 222 as shown in FIG. 2 in a state of plan view from above.
Therefore, as explained above, since the external shape of the optical unit 222 is formed in the square shape or the like because of the limitation in the processing method, as shown in FIG. 2, an area D as an outer circumferential area of the circle C is an optically ineffective area in the state of plan view from above. Therefore, a useless area is formed in the optical unit 222.
As shown in FIGS. 3 and 4, in general, in an insertion section distal end 231 of an endoscope, besides an image pickup unit 234, a light guide 235 for illumination, a treatment instrument inserting-through channel 236, and the like are provided around the image pickup unit 234. As shown in FIG. 4, an external dimension of the insertion section distal end 231 of the endoscope is determined by an external shape of the image pickup unit 234 itself and an external shape of the light guide 235 for illumination and the treatment instrument inserting-through channel 236. However, even in this case, if an optically ineffective area E is formed in the image pickup unit 234, the external shape of the image pickup unit 234 is increased in size. Therefore, the insertion section distal end 231 of the endoscope is increased in diameter. This may be a cause of pain for a patient.